In general, Raman fiber lasers include a pump source coupled to a fiber, such as an optical fiber. Energy emitted from the pump source at a certain wavelength λp, commonly referred to as the pump energy, is coupled into the fiber. As the pump energy interacts with the material from which the fiber is made, one or more Raman Stoke transitions can occur within the fiber, resulting in the formation of energy within the fiber at wavelengths corresponding to the Raman Stoke shifts that occur (e.g., λs1, λs2, λs3, λs4, etc.).
Typically, the fiber is designed so that the energy formed at one or more Raman Stoke shifts is substantially confined within the fiber. This can enhance the formation of energy within the fiber at one or more higher order Raman Stoke shifts. Often, the fiber is also designed so that at least a portion of the energy at wavelengths corresponding to predetermined, higher order Raman Stoke shifts (e.g., λsx, where x is equal to or greater than one) is allowed to exit the fiber. The energy at the wavelengths λsx can be used, for example, to enhance the signal in an optical fiber.